Gas burner

ABSTRACT

Gas burner provided with a plurality of concentric flame crowns, and comprising a first central burner to supply a peripheral flame ring, a second annular burner surrounding said central burner at a defined distance and able of supplying at least a respective peripheral ring, a burner body apt to be mounted on the surface of a cooking hob, a first gas inlet in communication with said body, a first vertical gas injector, said central burner being provided with a first chamber for the diffusion of the air/gas mixture, a second gas inlet in communication with said body, wherein said second annular burner is provided with two separate chambers for the diffusion of said mixture, wherein said second gas inlet is in communication with said two separate chambers through suitable injection and conveying means, which comprise two distinct injectors in communication with said second gas inlet, and two respective horizontal Venturi pipes each of which being able of supplying with said air/gas mixture a respective of said two diffusion chambers; these are physically separate and not in communication to each other. 
     Said two horizontal and separate injectors are placed on the same end position of said second gas inlet.

The present invention relates to an improved, preferably household gas burner, generally used in the cooking gas appliances.

In the following of this description it will be referred to a gas burner provided with both a central body with a peripheral flame crown, and a peripheral body provided with two flame crowns, oriented inwards and outwards, but it will be intended that what explained may be identically applied and therefore valid also for gas burners provided with only a peripheral body, that is without the central flame body.

Gas burners are known, provided with a plurality of flame crowns which assure an homogeneous distribution of the generated thermal power and therefore provide an uniform heating of the cooking containers/pans over them placed.

A particularly efficient embodiment of such burners is that one which comprises a central body and an outer annular body, said two bodies being basically circular, coaxial and separated to each other by a suitable distance which is horizontally extended, and obviously also shaped as a ring; as such burners are universally used, it is cited, only for documentation, the U.S. Pat. No. 6,132,205.

Such kind of burners have been experienced to be particularly efficient as they are able to generate, inside a limited surface, a high specific thermal power, just because they are based on the provision of grouping a certain number, preferably three, concentric flame crowns.

However such kind of burners are not deprived of some drawbacks which limit their use and performances; as a matter of facts they often show two injectors and two respective Venturi pipes, one feeding the central burner, and the other feeding the outer annular burner.

Moreover it is known that such arrangement allows the delivery thermal powers which hardly can exceed 4-4.5 kW.

It is also known that a Venturi pipe becomes more efficient when its length is proportional to the Venturi throat diameter, and it is also well known that the latter dimension determines the burner thermal power. As a consequence, to delivery large power, it is needed to provide long-neck Venturi pipes, able of sucking more air and to closely mixing said air with the gas.

As the central burner size is unavoidably limited, it would be in any case not able of providing a high thermal power; therefore the respective gas injector and respective Venturi pipe may be limited in their extension, and so the injector and the respective Venturi pipe may be normally oriented vertical, without causing a remarkable penalization.

As a matter of facts it is here reminded that the height of the cooking gas hobs, specifically for household use, must be comprised within well definite limits, usually 30 to 40 mm.; therefore a limited height of the Venturi pipe for the central burner turns to be also compatible with such height limit, and so the vertical orientation of the Venturi pipe which is shorter for the central burner becomes compatible both with its limited thermal power that can be delivered, and with its vertical height that can be admitted.

Different is the case of the outer annular burner; in such a case it is needed to deliver high thermal power, and this need hinders the bound of a properly prolonged and vertically positioned Venturi pipe.

In order to overcome such drawback it is known, for instance from the patents WO 2004/044490 A1, U.S. Pat. No. 6,132,205, WO 2005/073630 A1, WO 0712766 A1, WO 2005/078342 A1 to split the gas flow into a plurality of usually two or three separate and distinct injectors, and respective Venturi pipes which are obviously distinct as well.

As a matter of facts it is also known that the splitting of the gas flowing means (injectors and Venturi pipes) into a plurality conduits showing a lower delivery and so with a lower single thermal power, but also with shorter lengths, easily allows to reach and also to overcome the power of a single conduit (injector and Venturi pipe) having the same gas delivery as the sum of the gas deliveries of the previous conduits.

However even such conditions do not properly offer the best compromise between:

-   -   the wished minimum vertical size of said gas conduits,     -   the burner geometric shape and size, which appear to be         over-sized with respect to the cooking pots/containers,     -   and the maximization of the overall deliverable power,

as said conduits (injectors and related Venturi pipes) are in any case vertical, and the fact that they are vertical restricts their length, and therefore the deliverable thermal power.

Moreover, as said pipes must be lodged inside the burner, it turns that, when their number increases, the burner becomes more and more cumbersome.

This circumstance causes a performance decrease, as the heat is being transferred from the burner to the sides of the cooking pot, instead that on its bottom; as a consequence the heat transfer is obviously hindered, and the gas consumption and cooking time are experienced.

True it is that the cited WO 07012766A1 and WO 2005/078342 respectively show three and two conduits which are remarkably inclined on the horizon, but said conduits (injectors and Venturi pipes) are also originated on the burner central axis, and therefore they stretch radially for only an extension which is about similar to the burner radius, what limits their length, and consequently the deliverable thermal power; moreover the injectors positioning in the burner centre, i.e. far away from the burner side edge, obstacles the primary (A) and secondary (B) air inlets, due to the over-heating and of the consequent gas rarefaction.

In order to overcome such drawback, from EP 1120603 B1 it is known a kind of gas burner of the generally described kind, with three coaxial flame crowns generated by burners split into a central body and a outer annular body, wherein an injector and a respective Venturi pipe are arranged to feed the outer annular body and which are placed both in horizontal and for the whole extension of the burner lower diameter.

Such solution apparently overcomes the bound due to the limited extension in the length of the gas conduit, as it makes use of the maximum available extension; however in this case too it is not possible to deliver the maximum possible power as the gas conduit is only one, being not implemented any splitting in the gas conduits; as a consequence there is an apparent discrepancy between the horizontal arrangement of the gas conduit, which prolonging the Venturi pipe increases its power, and the singleness (no splitting) of the injector and of the Venturi pipe, which prevents the full exploitation of the available room to maximize the theoretically installable thermal power.

Moreover like solutions more precisely suffer the primary air rarefaction, caused by the heating induced by the working burner itself; this can be demonstrated by the presence of tips of yellow flames after about ten minutes from the burner ignition.

Furthermore the fact of placing said Venturi pipe in the centre of the lower burner portion apparently hinders, creating further functional and constructive problems, the injector assembly and the lodging of the related vertical Venturi pipe which feeds the central body and which evidently has to pass through the burner axis, which in the presently cited patent is instead taken by the horizontal Venturi pipe.

It would therefore be desirable, and is actually a main purpose of the present invention, to provide a type of gas burner provided with a central body and with a peripheral annular body separate to each other, which are provided with respective injectors and Venturi pipes, and which are placed not in vertical and are able of exploiting basically the whole burner cross size (width) in order to allow the lodging of a plurality of separate Venturi pipes, so increasing the overall deliverable thermal power, but still permitting to adjust the burner to another gas set up by replacing the injectors without disassembling any part of the appliance.

According to the present invention, this and further aims are reached in a kind of burner incorporating the characteristics as recited in the appended claims and including such operating means as described below by mere way of non-limiting example with reference to the accompanying drawings, in which:

FIG. 1 shows a perspective and exploded view of a burner according to the invention,

FIG. 2 shows a plan transparent and top view of a burner according to a first embodiment,

FIGS. 3, 4 and 5 show respective vertical views of the burner of FIG. 2, according to the respective sections A-A, B-B, C-C,

FIG. 6 shows the top plan view of the burner crown (particular 2 of FIG. 1) relative to the body of FIG. 2, without the covers of the chambers diffusing the air-gas mixture,

FIG. 7 shows a plan and top view of a burner according to an improved embodiment of a gas burner,

FIG. 8 shows a top plan view of the portion of the burner of FIG. 7, deprived of the covers of the chambers diffusing the gas,

FIG. 9 shows a schematic perspective view of the upper crown of the burner body of FIG. 8.

With reference to figures from 1 to 6, a gas burner according to invention, and typically devoted to fit out a cooking appliance, not shown, comprises:

a burner body 1 and an upper crown 2, which are connected by the layer 5 and covers 3, 4,

a first central and circular burner 6, per se known, able of feeding a peripheral flame crown 7,

and a second annular peripheral burner 8 which surrounds said first central burner 6 at a definite distance thereof, provided with suitable adducting means to the inner flame crowns, of secondary air (B), said second annular burner having one or more flame crowns which are either inwards 9, i.e. oriented towards the first burner, or outwards 10, or both said arrangements.

Said burner body includes, in a well known way, a conduit which acts as a first gas entrance 11, which ends into a first vertically oriented injector 12 and a related first Venturi pipe 13 which is vertical as well, which are designed and arranged to feed said first central burner 1.

According to the invention, the means to lead the gas into said second annular burner 8 comprise a second gas burner inlet 13 which enters said burner body and which reaches an end position 14, wherefrom two distinct gas paths are being originated, wherein each path comprises a respective injector 15, 16 and a respective Venturi pipe 17, 18.

Said end position 14 is practically arranged on the outer lower side of said burner body, i.e.: where said second gas entrance 13 enters the volume of said burner body, there it terminates to said end position 14.

Both said two injectors 15, 16 and the relevant Venturi pipes are horizontally oriented and basically they lie on the same plane of said second entrance 13.

Said two Venturi pipes 17 and 18 moreover do extend till the diametrically opposed portion of the burner body, with respect to said end position 14, and therefore from said zone said Venturi pipes admit into said gas diffusion chamber of the gas-air mixture, as it will be explained later on.

The man skilled in the art will have surely already guessed that with this simple solution the main purpose of the invention is reached, as:

the presence of the two injectors and related Venturi pipes implements the desired power splitting, which reduces the consequence of the over-heating on said yellow tips,

the horizontal orientation of the injectors and related Venturi pipes allows an efficient exploitation of the horizontal size of the burner body, avoiding the bound made by the maximum height let by the burner itself,

and even more the circumstance of extending the Venturi pipes from a side to the opposite side of the horizontal diameter of the burner body allows to maximize the Venturi pipes length what, as before reminded, allows to improve the deliverable thermal power and therefore to optimize the ratio between the burner size and the (high) power.

The just described solution allows some profitable improvements which further make easier the burner functional flexibility; a first improvement consists in the fact that said injectors 15, 16, branching out from said same end position 14, are logically oriented so as to show an acute angle “g” between them, as shown in FIG. 2.

Obviously even the two Venturi pipes 17, 18 are oriented in a way aligned with the respective injectors 15, 16, that is are angled between them, and this permits that in the axial, that is in central zone of the burner body, said two Venturi pipes be diverted at a certain distance, what allows the arrangement and passage between them of the vertical injector 12 and related Venturi 13 which, having to feed the central burner 6, have to be necessarily axially placed and therefore in a position between said two Venturi pipes 17, 18, as shown in the FIGS. 2 and 7.

The second improvement consists in that, in order to optimize the functional and productive features, the two injectors 15 and 16 and related Venturi pipes 17, 18 are symmetrically positioned with respect to a vertical symmetry plane, logically passing through the central axis “X” (see FIG. 4) of the burner body.

Said two Venturi pipes 17, 18 admit into respective gas diffusion chamber which are placed above through the conduits 19, 20, (FIG. 4) and provided with suitable ports leaving the air-gas mixture to flow out to be burned.

Advantageously said diffusion chamber is divided into two separate and not intercommunicating chambers 21, 22, through suitable vertical septa 23A, 23B, 23C, 23D, as shown in FIG. 6, and each of said Venturi pipe admit into only one respective of said chambers 21, 22.

Therefore the advantage is achieved that the combination of injector, related Venturi pipe and diffusion chamber actually implements a two burners assembly which are mechanically and functionally autonomous.

Moreover the presence of the two Venturi pipes and of the two related separate diffusion chambers, supplied with only one gas source 14 (FIG. 2), allows to improve the burner safety because in case of an injector occlusion any unburnt gas is prevented from lighting back into the burner itself.

As a conclusion it may be obtained not one but two peripheral and wholly independent burners, and such independence allows a much better flexibility both in the size and in the operation of each burner alone.

With reference to FIGS. 2, 4 the access of the two Venturi pipes into the respective chambers may be properly improved by providing the pipe fittings between said gas conduits with special deflection means 31 able to ease the air/gas mixture passage from the Venturi pipe into the respective conduits 19, 20 and to uniformly convey said mixture into the respective chambers 21, 22.

It is to be noted, in the facts, that the Venturi pipe of this invention is horizontal, as it is the diffusion chamber either, but this one is arranged at an higher level than the respective Venturi pipe.

Therefore a vertical portion of conduit has to be made, which implements a kind of connection able of driving the gas in the vertical direction between said two conduits (Venturi, chamber).

The transition from the horizontal Venturi pipe and said vertical connection may be carried out by a conventional bend of 90°.

However such solution causes, as well known, a certain aerodynamic resistance and a consequent gas swirling, what reduces both the flow rate and uniformity.

In order to avoid such drawback, said vertical connection is being properly provided with a specific deflector 31, which eases the change of gas direction and reduces the generated turbulence.

A further problem caused by the fact that said two Venturi pipes are very close and also little angulated from each other, and so they get the same peripheral portion of the burner body, and as each Venturi pipe has to enter the respective gas diffusion chamber, and finally as said two gas diffusion chambers 21, 22 are semi-circular, it comes as a logic consequence that said two Venturi pipes feed the respective chambers 21, 22 in two respective zones which necessarily are placed at respective extreme sides 21B, 22B of the respective chambers.

It was also realized, and it was also foreseeable by the man skilled in the art, that the fact of feeding the gas at the extreme side of each gas diffusion chamber causes an irregular gas distribution inside the chamber itself, which obviously compromises an even combustion and flame combustion.

In order to overcome such drawback, and with reference to the FIGS. 7 and 8, said Venturi pipes are so sized and angulated to each other so that they enter not into the extreme side of said respective gas diffusion chambers 21, 22, but in respective zones 21A, 22A (FIG. 7) which are remarkably far from said extreme sides 21B, 22B (FIG. 6).

This is logically possible by making said two Venturi pipes to sufficiently diverge, but avoiding that said provision would too much shorten the length of the same Venturi pipes.

However the fact of introducing the Venturi pipes into an intermediate zones of the respective chambers determines the need that the gas flow is being split into two separate, and basically opposed at 180° flows; as a matter of facts it is just what wanted, if it is whished that the gas entered into an intermediate zone of the relevant chamber be split into two flows, each of them goes into a respective portion the gas diffusion chamber.

But in this case the problem to change the direction of the gas flow into two opposed directions is raised, which causes a further gas turbulence.

In order to avoid the risk of sharp bending of the gas conduits 19, 20 too, what (as just explained) would harm the gas flow uniformity and delivery, on the terminal portion of the Venturi pipes respective symmetrical connections 25, 26 are arranged, having a double-face deflector, as shown in the FIG. 7. 

1. Gas burner provided with a plurality of concentric and preferably circular flame crowns, and comprising: a first central burner (6) able of supplying a peripheral flame ring, a second annular burner (8) surrounding said central burner at a defined distance and able of supplying at least a respective peripheral flame ring (9, 10), a burner body (1) apt to be mounted on the surface of a cooking hob (C), and including: a first gas inlet (11) in communication with said body, a first gas injector (12) whose axis (X) is vertically oriented, said central burner being provided with a first chamber (13) for the diffusion of the air/gas mixture, and with a plurality of ports to let said mixture out, placed on its upper edge (7) and whose top is closed by a first cover (4), a second gas inlet (13) in communication with said body, wherein said second peripheral burner (8) is provided with two separate chambers (21, 22) for the diffusion of said mixture, and with a plurality of ports (9, 10), to let said mixture out, placed on the relevant upper edge and whose top is closed by a second cover (3), wherein said second gas inlet (13) is in communication with said two separate chambers (21, 22) through suitable injection and conveying means, characterized in that said injection and conveying means comprise: two distinct injectors (15, 16) in communication with said second gas inlet (13), two respective Venturi pipes which are placed in horizontal (17, 18), each of which being able of supplying said air/gas mixture with a respective of said two diffusion chambers (21, 22).
 2. Gas burner according to claim 1, characterized in that said diffusion chambers are physically separate and not in communication to each other.
 3. Gas burner according to claim 1, characterized in that said two horizontal and separate injectors (15, 16) are placed on the same end position (14) of said second gas inlet (13).
 4. Gas burner according to claim 3, characterized in that said two separate injectors (15, 16) are placed in the lower portion and substantially in a side portion of said burner body (1), and are oriented towards the opposite side of the burner body.
 5. Gas burner according to claim 4, characterized in that said two horizontal injectors do reciprocally separate from said second gas inlet (13) with an acute angle (“g”).
 6. Gas burner according to claim 5, characterized in that said two Venturi pipes (17, 18) are symmetrically placed with respect to the vertical central axis (X) of said burner.
 7. Gas burner according to claim 1, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 8. Gas burner according to claim 7, characterized in that said deflection means are implemented through a bending oriented upwards and properly shaped and smoothed, arranged at the end of the respective Venturi pipes.
 9. Gas burner according to claim 7, characterized in that said deflection means are implemented through two opposed and properly smoothed bending (26, 27) arranged on the ends of the respective Venturi pipes (17, 18).
 10. Gas burner according to claim 2, characterized in that said two horizontal and separate injectors (15, 16) are placed on the same end position (14) of said second gas inlet (13).
 11. Gas burner according to claim 2, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 12. Gas burner according to claim 10, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 13. Gas burner according to claim 3, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 14. Gas burner according to claim 4, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 15. Gas burner according to claim 5, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 16. Gas burner according to claim 6, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 17. Gas burner according to claim 8, characterized in that said deflection means are implemented through two opposed and properly smoothed bending (26, 27) arranged on the ends of the respective Venturi pipes (17, 18).
 18. Gas burner according to claim 11, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 19. Gas burner according to claim 12, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18).
 20. Gas burner according to claim 13, characterized in that said two diffusion chambers (21, 22) are provided with respective deflection means (31) of the mixture flows coming from the respective Venturi pipes (17, 18). 